Telephone system



June 14, 1927.

A. ET HAGUE TELEPHONE SYSTEM Filed March 4. 1924 4 Sheets-Sheet 1 mwm HIJ..

June '14, 1927. 1,632,066

A. E. HAGUE TELEPHONE SYSTEM Filed March 4. 1924 4 sheets-sneer 2 June 14 1927. 1,632,066

l A. E. HAGUE TELEPHONE SYSTEM Filed 'March 4, 192/ l4 sheets-sheet 3 ffy J.

June i4. 1927. A. E. HAGUE TELEPHONE SYSTEM filed March 4. 1924 4. Sheets-Sheet 4 W. www* .Sv H

' tems wherein connections are established b Patented June 14, 1927. y

' UNITED STATES vPM?ENT,oFFifC-iai.

ALFRED E. BAGUE, OE BROOKLYN, NEW YORK, AssmNOE `To WESTERN ELECTRIC COMPANY,`I'NCOI trOEATED, OENEW YORK, N. il.; A CORPORATION OE NEW vom;

TELEPHONE SYSTEM.

This invention relates tortelephone. sysmeans oiimeclianically `controlled switches,

and more particularly to such a telephone system wherein Atrunks are providedbetween abranch exchange and a central oice.

ln machine switching telephone ,systemsV heretofore devised with which the-applicant is familiar. the link or trunk circuit between the branch exchange and the central office has not been madebusy at the distant end;

until an appreciable interval ol time has elapsed after its seizure at the originating end', Oltcn times resultingV in double seizure of the same trunk result-ing in considerable confusion. .another difficulty heretofore experienced has been that the busy condition was removed before the trunk circuit was fullyy restored to normal, hence if. the trunk was again seized under suchl conditions, the new call would frequently :tailto progress., and the old connection might not be fully broken down. Another diiiiculty experienced in existing machine switching systems has been that the false initiation of a call duc to a trouble condition upon the connect- `ing link kor trunk circuit has caused one of a group oil' first link `circuits (line switch or `line iiiider,etc.,) to be seized and thus rendered unavailable to lines initiating regular calls. .Another ditliculty experienced in some machine switching systems is thatafter a call has progresed to a certain point, the4 switches `are disconnected and vthe line returned to normal ,it the call fails to progress any further. It thecall was falsely initi ated by a trouble condition which (as usu. ally occurs) was insufficient to `cause it to progress properly, the call would again be initiated after the switches returned to normal and the switches would again be seized andV again released. This cycle of ,operay tions usually termed pumping would continue until an attendant removed the cause of the trouble or put t-he 4defective line out `of service.

The Object o1 this invention is to so iinprove the rcircuits between the branch exchange and the central office as to eliminate the difficulties enumerated.

In accordancel with this invention, a. relay connected to 'the trunk Circuitat the branch exchange causes the trunk to ,test busy im mediately after it yisHseiZ/ed at the central oiiice and to remain busy until the switches y at the central office are'properly dismissed.

F u'rtliermore a combination of relays con nected to the trunk at the central oifice pre-w vents the connection from being built up unless the signalsrec-eived roin'the branch eX- change over the trunk conductors' are the Iequivalent of those requiredv to initiate a regular` call, but in case the'call was vfalsely initiated-by a trouble condition will hold the defective trunk circuit in a locked condi# tion, thus avoiding the trouble known as pumping.` l

Fig. l diagran'iinatically represents thc branch exchange end of a trunk circuit which is only accessible todial stations, and

. which is merely intended to be used for one way traiho (calls outgoing from the dial stations to the central oiiijce). Fig.. 2 diagrammatically represents the essential `apparatus. and circuits required at power drive system.

Fig. v3 diagrammatically represents the yessential apparatus and circnitsrequired at the central oilice in a step-by-step machine kswitching system such, for example, as the Strowger type. f

. Fig. at `diagrammatically `represents ,the branch exchange end of a trunk circuit which `is accessible eitherv to the `dial station or to the P. manual switchboard and which is intended to be used` for traiiic in Yeither direction, the calls incoming` i'roin the central yo'liice" to the P. B. X `being handled by the operator at the P. B switcliboard., A

The Strowger syst-em and the power drive system are both Aso well known in the art X. manual that neither system will be described in full detail in this specification.

are described very fully in the Automatici Telephony.` i Campbell, Vsecond edition.

work entitled by Smith and The Ipower drive system is likewise disclosedand described in the patent to Frank S. Irvine, No. 1.541,356,

granted J une'l9, 1925, the .patent vto Franklin A. Stearn, No. 1,505,571, granted August m1924- Y r The invention may readily be adoptedto other `machine switchingsystems but as the twogsysteins speciically referred kto herein Vare typical, it is believed that thermethod ofnapplyingithe invention to other systems will ibereadllly discernible.

Both systems y 1t is believed that the invention and its application will be fully understood from the detailed description which follows:

The invention niay be used in a full inechanical step-by-step niachine switch system in which case Fig. 3,will be used in conjunction with either Figs. 1 or 4. `When twoway traliic is desired, Figs. 4 and 3 are used in combination and when one-way traffic only is required, Figs.' 1 and 3 are used in combination.

Figs. L and 5 a cmnfbnatz'on.

@all from dial Szfafon o central Officef lVhen the receiver at the dial station 416 is removed froni the switchhook and the dial 458 is operated in accordance with the digits comprising the centra-l ofiice code; the selectors S and S-'l are set extending the line from the calling station 416 to operate the relay 405 as follows: battery, winding of relay 405, 417, 451, 441, 431, 421, station 416, 420, 430, 440, 450, 413 to ground. Relay 405 operated, operates relay 412 over a circuit froni battery, 426, 425, 424, 423, 419, winding of relay 412 to ground, and connects ground tl'irough the resistance 443 and winding of relay 401 to conductor 447 of the trunk, and solid ground to conductor 444 of the trunk for a purpose hereinafter described. Relay 412 operated, connects .solid ground to the terininal 452 of the selector S-l by way of conductor 434, to prevent the .selector switches S and S-l freni releasing, and operates relay 411 over an obvious circuit. Relay 411 operated, operates the busy signal 410 and the relay 404 in parallel over obvious circuits. 'lhe signal 410 operated, indicates to the operator at the P. B. X. manual switchboard that the trunk with which the signal is associated is busy. Relay 404 operated, opens at 429 the conductor leading to the circuit of relay 407 to prevent it from operating falsely in case relay 403 should be momentarily operated. A

Solid ground connected to the trunk conductor 444 closes a circuit to operate line relay 311, (Fig. 3) over a circuit as follows: battery, winding of relay 311, 32.9, 328,

437, 436,435, to ground. Relay 311 operated, closes an obvious circuit to operate relay 310 through its lower winding. Relay 310 operated, causes the plunger 307 to plunge and close the leads connected to the various sets of springs 367, 306; 336; 356, 355; to establish circuits which will hereinafter be incre fully described. The operation of relay 310, opens at 329 the circuit for the line relay 311 vbut the latter being slow to release does not open the circuit through the lower winding of relay 310 until the circuit for the upper winding of' the Same relay has been' established,-

manner hereinafter described. A circuit is now closed to operate relay 309 as follows: battery, winding of relay 309, 333, 334, 335, 33.6, 337, 338, 339, upper winding of relay 302, 343, 344, winding 312 of the dial tone transforn'ier DT to ground. Relay 302 operates over a circuit as follows: battery, lower winding of relay 302, 353, 354, 355, 356, 357, 328, 327, 326, 325,324, 323, 445, 444, 443, 439, 438, 437, 436, 435 to ground. Relay 302 operated, closes a circuit to operate relay 304 as follows: battery, winding of relay 304, 363, 359, 358, 303 to ground. Relay 304 operated closes the holding circuit for relay 310 heretofore referred to as follows: battery, upper winding of relay sie, ses, eee, am, 366, 364, 365 t0 ground. This closure provides a substitute circuit to hold relay 310 operated after relay 311 releases. Relay 309 closes a testing circuit which if closed causes relay 300 to operate as follows; battery, winding of relay 300, 345, 346, 347, 348, 349, 446, 447, winding of relay 401, resistance 448, 438,437, 436, 435, to ground. vrelay 401 may or may not operate over this circuit depending upon the resistance of theV trunk cable conductor 446 between the P. B. X. (Fig. 4) and the central oilice (Fig. 3). Relay 300 operated, locks through its own contact 345, and armature 36.9 by way of 368, 306, 367, 366, 364, 365 to ground; closes an obvious circuit to operate relay 305; connects solid ground to the sleeve terminal 319 associated with the trunk at the multiple bank of the connector C-l, causing the trunk to test busy to any connector which may be testing this trunk at the time; extends the Vcircuit from the f. B. X. (Fig. 4) to the impulse relay 302 (Fig. 3) hereinafter described. ,lf the testing circuit; traced is not closed due to a trouble condition on the trunk, relay 300 will not operate and the l?. B. X. trunk circuit (Fig. 4) will not be linked to the inipulse relay 302 of the selector circuit (Fig. 3) and the call cannot progress any further.

Relay 305operated, opens at 333 the circuit through relay 309 which releases.

Having linked the trunk from the P. R. X. to the selector' S2, we are new ready to extend the connection through to the calling dial station 416 (Fig. 4) and to indicate to the station 416 that the circuit is in condition to dial the number of the called line which we will assume to be the station 318. lt tirst necessary to operate relay 400 and this is accomplished as hereinafter dcscribed. A circuit is new closed to operate relay 401 as follows: battery, lower winding of relay 302, 353, 354,355, 356, 357, 328, 349, 446, 447, winding of relay 401, resistance 448, 438, 437, 436, 435 to ground. Relay 401 operated, closes an obvious circuit to operate relay 402 which in turn closes another obvious circuit to operate relay 406.

pletes the connection 4between the calling station 416 `(Fig. 4) andthe selector S-2.

3); opensthe circuit through `relay 405 whichreleases; provides at its armature 455 a substitute path, to holdthe `relay 412 operated after relay 405 releases,

llVith the connection established between the `calling, station 416 and the selector S1-2,`

the impulse relay 302 is connected in series with thecalling line in the usual manner and theinterrupted current produced in the winding 373 oi vthe dial tone transformer DT (froma source not shown) induces a similar current in itswinding 312 which is in series with the calling station 416. This interrupted Current produces a tone in the receiver of the calling station 416 as an indication that the circuit is in condition t'or dialing'. n l

lllhen the dial 458 of the calling station 410 (Fig. 4) is operated and released, tn'e circuit at the calling station 416 is interrupted and the impiilsesthus produced are .transmittedy to impulse relay 302 (Fig. 3)

which-follows the impulses. Each time relay 302 releases a circuitvis closed to operate primary magnet 317V over a circuit as follows: battery, winding of primary magnet 317, winding oi-relay 308, 375, 374, 376, 359, 358, 303 to ground. Brushes 320 to V322, inclusive, are moved by successive steps in accordance with the primary movement ot the selector S-2. Duringthe'iirst step of Vthe brushes I320 to 322, inclusive, the off- Relay 308` normal contacts ON are closed. operates in series-with the primary magnet 31,7 the first time the impulse relay `302 releases but relay 308 being slowto release remains operated throughout the impulse period.

As soon as the oif-normal contacts ON' Relay 315 operated, locks as follows: bat-- tery, winding of relay 315, 377, 382, 383, 358, 303 to ground. The primary movement ,of the switch is completed'at the end of the impulse train and the impulse rel'ayi302 remains operated opening the circuit through the primary magnet 317 and relay 308, releasing the magnet andthe relay. In releas ing, relay 308`closes a circuit to operate the Vsecondary magnet 314 as follows: battery,

winding ofxsecondary magnet 314, `384, 380, 379, 364, 365vto ground. Theoperationof `the secondary magnet initiatesthe secondary movement of the ,selector switch S2'caus1ng the brushes 320 to 322, inclusive, to advance one ystep to the, terminals .,ofvthe first "trunk net 314 in operating opensat its 'contact 382 the locking circuitfor relay 315 previ;` ously tracedreleasing relay 315. If the lirst trunlr is busy, solid ground on the sleeve terminal (corresponding tothe terminal 3,32) will be connected to tlie'biush 322. The

i'eleaseof relay 315 opens the voperating circuit (previously traced) of the secondary magnet 314 whichlilrewise releases. A cir- (.uitwill now be closed .by way of the sleeve terminal of the busy trunk to reoperate relay as tollowszbattery, winding of relay 315, 377, 382,385, 386, 387, 388, 322, terminal corresponding to 332, toground. Relay 3,15 operateth-locks `over the locking circuit previously traced and closes tliecircuit previously `traced for the secondary magnet 314.

of the selected group. The secondary mag- The seconda-ry magnet .314 again operates, advancestlie brushes 320 to 322 to the teri'ninals ol the next trunk in the group and again opens at 382 tlielocking Vcircuit for the relay 315, releasingthe relay which in turn opens the circuit through Athe secondary ee l inclusive, are no w resting uponA the termi- 1 nals 330 to 332, inclusive and that the selecn tor switch S-3 is idle in which case the terminal 332 will be free from ground. A circuit will now be closed to operate the relay 301 as vfollows: battery winding of relay 315, 377,382, 385,winding of relay 301, 366, 364, r3,65 to ground. Relay 315 will not operate lat this vtime due tothe high resist-ance of the winding of relay 301 in series with it. Relay 301 operated, extends the connection by way of the brushes 320 to 322, inclusive, to the selector switcliS-3. The impulse relay, not shown, of the selector switch S-3 will operate', operating a slow relay, not shown, in the selector switch S-3 which will cause solid ground to be connected to the terminal 332. .The relay 301 operated epens at 339 and, 353 .the circuit through the impulse relay 302 which releases and 'in turn opens the circuit `through relay 304. Relay`304 being slow to release,V does not release immediately but remains oper-- ated longl enough-for the slow relay, `not shown, in the selector switch S-3 to operate and Aconne-ct ground-to the terminal 332.

Relay 301 now locks over the following cir- -of Iterminal 332, 388, 387, and 390 under control of relay 301. The selector switch S- 3 operates under control of the dial 45,8 of the 'calling station 416 in' substantially .the same l UU manner as the selector switch S-2, and eX- tends the connection to the connector C which likewise operates under control of the dial 453 of the calling station 416 to complete the connection to the called station 313.

The called sta-tion 318 is signaled in a manner not shown, and upon responding establishes the talking circuit between the callin and called stations. Battery to maintain the relay 401 (Fig. 4) operated is supplied by the connector C in a manner not shown.

HoZcZfzayHSo long as the talking circuit is established and the loop is closed at station 416, the impulse relay (not shown) in the connection C and the relay 401 remain operated in series. So long as the impulse relay in the connector remains Voperated the switches cannot release. Relay 401 holds relay 402, which in turn holds relay 406. Relay 406 holds relay 400, which in turn, holds relay 412, the latter maintaining relay 411 operated. The busy condition is accordingly maintained at terminal 452 of the selector S-l, at the terminal 319 of the connector bank C-l, and the busy signal 410 at the manual switchboard likewise remains operated. Thus, intrusion upon the connection either at the terminal bank of the selector S1 (Fig. 4), or the connector bank C-l (Fig. 3), or at the jack 414 in the manual switchboard (M. S. B. Fig, 4) is prevented.

Flashing-Should the calling station 416 momentarily operate the switchhook, relay 401 will release, inturn releasing relay 402, which in turn opens the circuit to release relay 406. Meanwhilel the release of the switchhook at the calling station 416 causes relay 401 to reoperate, reoperatingrelay 402. Relays 402 and 406 are designed to be slow to release to prevent relay 406 from releasing when the switchhook is thus momentarily depressed.

Disconnect-Then the receiver is replaced on the switchhook at the calling station 416, relay 401 will release in turn releasing relay 402 which in turn releases relay 406. The release of relay 406 opens, the circuit through relay 400 which releases, thus opening (at 470 and 471) the talking circuit previously established between the calling and called stations. Relay 409 is now connected (at 472 and' 473) in bridge across the conductors 444 and 447 of the trunk operating relay-409. Relay 409 operated, furnishes a substitute holding path to prevent relay 412 from releasing when the battery, supplied at armature 455, is removed by the release of relay 400. Relay 412 is designed to be slow to release so that it will remain' operated while one holding circuit is being opened and another `is being substituted relay 412 will remain operated, consequently the calling station will remain locked to the trunk circuit by way of the selector switches S and S-l and the busy signal 410 will continue to be displayed before the operator at the manual switchboard (Fig. 4). Relay 409 remains operated in series with the impulse relay (not shown) of the connector circuit C (Fig. 3); but due to the highresistance of relay 409, the impulse relay in the connector circuit C releases, releasing the connector switch C in a manner which is so well known in the art that it is not shown in the drawing and will not be described in detail here. The release of the connector C removes battery from the conductors 445 and 446 (Fig. 4) and ground from the terminal 352 of the selector S-3 (Fig. 3).

Removing battery vfrom the conductors 445 and 446 releasesl relay 409 opening the circuit. through relay 412 which in turn releases. Relay 412 released, opens the circuit Jr'or relay 411 which releases. Relay 411 released, opens t-he circuits for the busy signal 410 and the relay 404, releasing relay 404 and restoring the busy signal to normal at the manual switchboard. In order to retain the busy condition at the sleeve ter minal 452 of the selector S-1 as long as possible ground is connected to the conductor 434 by way of 460 and 461 after relay 412 releases and as long as relay 411 remains operated. The release of relay 411 removes ground from the conductor 434 allowing the selectors S and Sel to release and restore to normal.

llfhen the ground was removed from the terminal 352, the selector switch S-3 was restored to normal in' a manner not shown. At the same time, the circuits for relays 301 and 310 of the selector S-2 were opened, releasing these relays. The release of relay 310 causes the plunger 307 to release, separating the various pairs of contacts 367 and 306; 335 and 336 and 356 and 355. The release of relay 301 closes a circuit t0 operate the release magnet 316 as follows: battery, winding of release magnet 316, 381, 304, 376, 359, 358, 303 to ground. The release magnet operates causing the rod of the selector switch S-2 to restore to normal. lVith the switch in the normal position contacts ON are separated opening the circuit through the release magnet 316 which releases thus fully restoring the circuit to normal.

AZZ trunks busy- If all the trunks in the group had been busy at the time the selector S-2 was hunting for an idle trunk, the brushes 320 to 322, inclusive, would have stepped from trunk to trunk'until they arrived in the all trunks busy or eleventh step position (assuming the trunk group to conysist of ten trunks). With the switch in this position the trunksbusy contacts TB` would be operated thus opening at 343 andV 344 the conductor to the winding 312 of the dialv toneftransformer DT and 'closing atv 343 and 391 the conductor leading the winding y313 of the busy tone transformer BT. This change in the condition of the circuit, changes the character of the tone produced in the telephone receiver at the calling sta` 'tion 416, from what is known as a dial tone to a' busytone, whicli'th'e subscriber at the station 416 will readily recognize and Whereupon thereceiver of the calling station 416 would be replaced on the yswitchhook re`` storing the circuit to normal in the manner previously described.

"Pumping of senden-4f the system were arranged so that when relay 309 operated as described under Call from dial stationto central office a local circuit was closed toV at this` time unless either ground is now pres" ent upon conductor 349 or afloop circuit is present across 'the conductors 323 349.4 f` It neither of these circuit conditions Vis pres` ent, relay 302 releases in turn releasing slow-to-release relay304 which `in* turn reify leases rclay310. Therelea-se of relay310 re# leases the line switchand any other relays which are operatedfalsdrelease, restoring the selector switch S-2 (Fig. 3) to normal. t

.Vlien 'the selector is restored to normahthe circuit to operate relay 311 is-agam vclosed over trunkconductor 323 in the rnannerpre-y viously described and tliecycle of `operations is repeated. The cycle of operations de# scribed is known as pumpingthe sendert..A T"

to "central 'o'yica-LfWhentlieplug ot a cord A circuit (not shown) is inserted in 'the jack' at -the manual switchboard M. S. B'.' relay 411 operated over anobvious circuit to ground at the contact 415 ofthe trunk jack.v Relay 411 operated, connects ground at ,460i 'to thetest terminal 4520i the selector S-l by way of the conductor 434 causing the trunk circuit to testbusy at the selector multiple bank.v Relay 404' and the busy signal 410 are operated in parallel over obvious circuits, the' :latter indicating at the manual-'switch board that the `trunk is busy. Thecord circuit (not shown) is provided with a bridge which loops the jack springs 462 and 463` together. A circuit is'now closed -to operate relay 405 as follows: battery, Winding of relay 405, 417, 464, 465, 463, through the bridge inthe cord circuit (notshown) 46,2, 466, 418

- to ground. Relay 405 operated, closes a'. cir' y cuit to `operate relay 412 and from this point 'on the-circuit .functions 'inthe' manner pre-f" viously described under Call from dial station to central oliice.

Flashing-The operator at the vmanual switchboard may withdrawthe plug of the cord from the trunk jack momentarily'in which case the circuit functions in the manner previously describedunder VF lashing in Call from dial station to central office. Disc0naect.Wlien the plug of the cord is removed from 'the trunk jack (Fig.y 4) at the manual switchboard, disconnection takes place in the general manner previously described under Disconnect-Call from dial station to central office. 'Call 'incoming from' central Ofic@ to P. B. X. manual switchboard-On an incoming call` (either local or toll) from'the central ollice, a connector circuit (not shown) estab lishes connection with the terminals indicated at C-1 (Fig.v 3), closing a circuit by wayof the test terminal 319 to operate relayV 305. VRelay 305 operated, prevents any of the relays associated with the line switch cir! v vcuit from operating, thus avoiding any possibility of a false connection with a selector switch ksuch as S-2. With a connector cir cuit connected to the terminals C-l, a circuit isclosed byway of leads 445 and 446 to opera'te the relay 409 which isy at this time` bridged across the trunk `conductors 444 and 447. VRelay 409 operated, closesvan obvious circuit to operate relay 412v which in turn closes another' obvious circuitl to operate relay 411. Relay 412 operated, also connects solid ground by way ofthe conductor 434 to the test terminal'452 of the selector switch S-l, causing the `trunk circuit to test busy immediately at the selector multiple bank (Fig. 4). Relay 411V operated, operates relay 404 and the. busy signal 410 in parallel over obvious circuits, the latter indicating to the operator at the manual switchboard that In case the call Vis incoming from some lo- -cil` point, signaling will take place immedi'- ately the connector'(not shown) establishes connectionwith `the terminals C-l. lf, how- V, ever, the call is incoming from a toll Voiiice.l

signaling will not commence until atter the toll operator has' received the proper ring ing signal whichV will not occur until the circuit for signaling the manual switchboard ,is fully established.` It is necessary, howi da ever, to cause the trunk to test busy both` at the manual switchboard'and at the-multiple` `bank of the selector S-l (Fig. 4) immediately the trunk is seized by the connector at the terminals C-1, to prevent the possibility of a false trunk seizure. vThis is accomplished inrth'e manner already described.j When signalingrcurrent is applied to the trunk by` wa'yof the connector circuit (notr shown) relay 403 which is bridged inseries with condenser across the trunk conductors v444 and 44Topera'te`s, openirrglthe-circuit through l ist relay 404 which releases closing the circuit to operate relay 407 traced for. convenience as follows: ground, winding of relay 407, 429, 467, 468, 454, 428, 427, to battery. Relay 407 locks under control ot relay 406 and closes at its contact 469 an obvious circuit to light the trunk lamp 41.3 as a calling signal. Relay 407 operated, opens the circuit lor relay 409 which releases, but relay 412 which was previously operated under control ot' relay 409 does not release as a substitute holding path is furnished by way ol: conductor /19 and contact 470 of relay 407.

Upon observing the lighted line lamp, the operator at the manual switchboard inserts the plug of a cord (not shown) into the trunk jack closing at its contact .415 a substitute holding path for relay 411. The relay 405 now operates in series with the bridge ot the cord circuit (not shown) in the inanner previously described in Call from 1 B. X.. manual switchboard to central oiiice. Relay 405 operated, connects the resistance 448 in bridge across the conductors 444 and 447 o't' the trunk, in order to remove automatic ringing.. (where used) from, and to operate the supervisory relay in, the con-- nector circuit (not shown) (Fig. Relay` 401 operates in series withthe resistance 448 iiroin battery furnished from the connector switch (not shown) (Fig. Relay 401 operated, operates relay 402 over an obvious circuit which in turn closes ,another obvious circuit to operate relay 406. Relay 406 operated, opens the locking circuit torrrelay 407 which rel-eases, and closes an obvious circuit to operate relay 400. Relay 407 released, extinguishes the line lamp 413. Relay 400 operated, establishes the talking circuit between the central oilice and the manual switchboard and opens the circuit through relay 405 which releases.

From this point the circuit functions in the manner previously,described under Call from dial station to'central oilice.

Figs. l cmd. 3 n combination-Figs. 1 and 3 may be used in conjunction where it is only desired to have traflic in one direction, nainely, from the dial station at the l). B. X. to the central oilice. 1 lVhen Figs. 1 and 3 are thus used in conjunction, removing the receiver at the calling station 115 (Fig. 1) operates a line switch (not shown) to extend the calling line to the selector switch S-f. The necessary central otlice code is dialed at the calling station 115 and the selector switches S-4 and S45 are set to extend the calling line to the outgoing trunk circuit shown in Fig. 1. With the switches thus set, 'a circuit is closed to operate relay in series with the calling line. Relay 100 operated closes an obvious circuit to operate relay 102; connects solid ground at 108 to' the conductor 109,

winding of 106 to the conductor 119. The line relay 311 (Fig. 3) now operates by way of conductors 323 and 109 to ground at 108 under the control of relay 103. The operation of relay 102 connects solid ground to operates through its lower winding via conductors 323 and 109 to solid ground at 108 under the control of relay 103. Relay 302 operated, closes an obvious circuit to operate relay 304. Relay 309 operated, closes a cir- 5L cuit to operate relay 300 by way of 345, 346, 347, 348, 349 and 119, relay 106, resistance 107, 108 to ground. Relay 300 operated, locks at 369 to ground at 365 under control of relay 304. Relay 106 may operate in series with relay 300 but will operate in series with relay 302 after relay 300 operates and extends the trunk circuit (Fig. 1) to the selector switch S2. The operation of relay 106 operatesrelay 104 over an obvious circuit. Relay 104 operated, closes obvious parallel circuits to operate relays 101 and 103. Relay 103 operated, locks under control of relay 102 and removes ground at its armature 108 from the trunk conductors 109 and 119. Relay 101 operated, extends the calling line by way of the outgoing trunk circuit (Fig. 1) to the selector switch S-2k; provides a substitute path to hold the relay 102 operated after relay 100 releases;

Elli

opens the circuit through relay 100 which releases removing the shunt formed by the resistance 107 from across the conductors 109 and 119. The dial at the calling station is now operated'and released in accordance with the digits of the number of the called line 318 (Fig. 3) and the selector switches S-2 and S-3 and the connector C are set to extend the connection to the called line in the manner previously described under Figs 4 and 3 in combination. Y

The called line 318 is signaled Vin a manner not shown, and upon responding, the talking connection is established.

Flashing-Then the calling station 115 flashes, relay 106 releases, opening the circuit through relay'104, but the latter which Disconnect-Jima) the receiver is replaced on the switchhook at the calling sta- .tionj115, relay 106 releases, opening the circuit vthrough` relay 104 which releases, in

turn, reieasing relay 101. Relay 105 is now connected in bridge` with the conductors 109 and 119 by way of armature 117 of relay 101. Relay 105 operates in 'series with the `impulse relay (not shown) in the connector C, thus providing a substitute pathA to keep relay 102 from releasing when relay 101 releases.. Relay 102 is designed to be slow to release, so that it will not release imme-' diately in case its holding circuit is .momentarily opened, while a substitute circuit is being provided to keep it opeiated. Relay 102, accordingly, remains operated, prevent. ing the selector switches S-4 and S-5 from `releasing and maintaining the busy condition'on the test terminal 142 of the selector S-5.

The impulse relay (not shown) in the con-V nector circuit C (Fig. 3) will release dueto the high resistance of the winding of relay 105 (Fig. 1) in' series with it. The release ot' the impulse relay allows the connector C to release and restore to normal in a manner not shown. S-S now release in the manner previously described. When the connector C releases, the

` circuit through relay 105 is opened and this relay releases. Relay 105 released, opens the circuit through relayk 102 which releases, removingtheholding ground from the test terminal 142 of the selector switch S-5 and allowing the selector switches S-4 and S-5 to ,release and restore the circuit to normal. Y

,The invention may also be used in conjunction with a full mechanical. power driven machineswitching system, in which case Fig. 2vwill be used in conjunction with either Fig.; 1 or F ig.- 4. When two way traflic'is desirable, Figs. 4 and 2 are used in combination and when onlyone waytraflic is required,Figs.j1 and 2 are *used in combi-1 nation.

Figs@ and 2 z'fn. combinaties.. y UaZZ'frmn-'dfial station to central oyjcep- W lien the receiver at the dial station 416 is" removed fromr the switchhook -and the dial 458 is operated in accordance with the digits comprising the central office code, the selectors S andS-luare sete-Xtending the line from thecalling station 416 to the relay 405,

andthe outgoing trunk-,circuit (Fig. 4) :functions in the general manner previouslyA described under Figs 4-and 3 in combination. over the trunk conductors 445 andA 446 to the circuit shownin Fiff. 2 and relay 206 operatesV over a circuit as follow-s z' battery, winding v of relay 206, 246,236,236, 237,233, 4145, 444,

443, 439, 43s 437, 436,435 to ground.' Relay 206 operated closes a circuit (not shown) in the line iinderLF causing the kbrushes 240 to2/12, inclusive, `or the line finder LF to `hunt Jfor the calling line. VWhen the brushl P242 engages with vthe terminal 232 of the The selector switches S-2 and The connection is now extended` calling line, `a circuit is closed to operate relay 202 by way` of brush 242 and terminal 232. The line finder isset upon the terminals 230 to 232 of the calling line yin a manner not shown herein, but which is fully describedin the patent to Frank S. lrvine, No. 1,541,356, granted June 9, 1925, and the patent to Franklin A; Stearn, l\To..1,505,571,k granted Aug. 19, 1924. Relay 202 operated, opens at`246 the circuit tlirough relay 206 wliichieleases. With the brush 242 of the line iinder switch LF connected to the terminal of the calling trunk, a busy condition is provided at the test terminal 220 ofi theI iinal multiple FM` by way of y243 and 244 ,to preventthe calling trunk from bein seized by a switch at the fina-lmultiple F l\ during the progress of a call incoming from the central-office to the P.' B. X. (Fig. 4). A ycircuit controlled by the` line vfinder-LF and district selector' DS is now closed to op-r crate the sender selector SS (in a manner not shown but fully described in the art cited), causing the sender selector SS'to huntfor and link an idle register sender to the line finder LF and district select-or DS, l

Y An obvious circuit is nowclosed to operate y relay 211 Vby way of terminal 262 andbrush i `Relay, 211 operated, connects ground by wayofits armature 254, lead 255,t'ermi` najl 256, and brush 217 to the niotor magnet 208V which operates opening at its armature 257 the operatingcircuit traced and causing theinotor magnet208 to release.` The releasei-o'fthe motor `magnet20-l causesthe brushes 217 to 219,V inclusive, to rotate one step in aclockwise direction over aterminal in each of the arcs1214 to 216, inclusive..`

With the motor magnet released and the brush 217 at rest uponV the next terminal of the arc the operating circuit for the motor ff magnet 208 is again closed and thecycle of operations is repeated, and provided relay `1 211 remains operated, the brushes 217v to 219 inclusive, will continue-to rotate vuntil the` brush 217rests'upon the terminal258 ofthe arc 214 when the operating "circuit for the motor-f. magnet 208 is opened. When -thef register sender RS is linked to the line findery LF circuits are'closedto operate relay 201 by Way of its right winding in serieswith relay 207, andr to operate relay 210 over a circuit as follows: battery,fwinding of the impulseI relay 210,v 260,125.0,y 241., 236, 237,- 233, 445, 444, .443,l 439,v

436, 435 to ground. Relay 210 operated, closes an obvious circuit to operate relay 209. lelay 201 operated, closes an obvious circuit to operate relay 205 maintaining a busy condition on the test terminal 220 at the final multi ale FM by way of 243, 245, 247 and 248. lxelay 201 now locks through its left hand winding by way of 25S and 259 to battery at brush 242 of the line finder LF. A circuit is now closed to operate relay 200 as follows: battery, winding of relay 200, ses, aai, 225, eee, asi, 44e, ai?, winding of relay 401, 44S, 438, 437,y 436, 435 to ground. Relay 200 operated, locks by way of its armature 22(- under control of rela.Y 205. rlhe relays in the outgoing trunk circuit (Fig. 4) now function in the manner previously described under Figs 4 and 3 in combination7 and the calling line 416 is extended by way of the trunk conductors 444 and 447; 445 and 446; 233 and 234; 235 and 236 to the impulse relay 210 and the relay 207. The calling station 416 is now in series with relays 210 and 20T, and may now control the impulse relay 210 by means of the dial S. f The dial 458 is operated in accordance with the various digits of the number of the called line 213 and the various tra-ins of impulses produced by the dial 458 cause the impulse relay 210 to release and reoperate in unison therewith. Each time relay 210 releases, a circuit is closed over the impulse lead 228 by way of 229, 264, 265 and 266 to ground. The registers (not shown) are set in sequence. by way of the impulse lead 22S under control ofthe impulse relay 210. The method of registering the impulses produced by the dial 458,.of setting the switches DS, IS, and FS (Fig. 2) and of signaling the called line 213 forms no part of this invention and will not be described herein. A complete explanation regarding the method of accomplishing these functions is given in the Aart cited.

Dismissing the SendGn-Vhen selection has been completed the circuit through relay 211 is opened in a manner not shown but which is fully described in the art cited and relay 211 releases, closing by way of its armature 254, lead 249 and brush 218, a circuit to operate the motor `magnet 208 which is thus restored to normal. The circuit through the impulse relay 210 is likewise opened in a manner not shown., releasing relayV 210, which in turn releases relay 209. A circuit is now closed in a Vmanner not shown but fully described in the art cited, causing the sender selector SS to function and restore to normal. f

`The talking circuit is now established and remains established as long as the receivers atl the calling and called stations, 416 and 213,1 remain olf the switchhoolrs.l

IfZaSLing.-lVhen-the calling station416 ashes, the ,outgoing trunk circuit (Fig. 4)

functions in the manner-previously described under Flashing7 (Figs. 4 and 3 in combination).

Disconneci-VVhen the calling station 416 disconnects the outgoing trunk circuit (Fig. 4) functions in the general manner previously described under fDisconnect (Figs. 4 and 3 in combination) and relay 409 operates in the usual manner to prevent the selector switches S and S-1 from releasing. The selector switches DS, IS, and FS, and the line finder LF release, removing battery from the trunk conductors 445 and 446 allowing relay 409 to release. After relay 409 releases, the selector switches S and S-1 and theoutgoing trunk circuit (Fig.` 4) restore to normal in the manner previously described.

@all from P. L. X. man/ual switchboard i0 central Unicef-The outgoing trunk Circuit (Fig. 4) functions in thegeneral manner previously described on a Ca-ll from l?. B. X. manual switchboard to central office (Figs. 4 and 3 in co1nbination7). The circuit shown in Fig. 2 :functions in the general manner previouslydescribed under Call from dial station to central oflice (FFigs. 4 and 2 in combination).

@all incoming from central office to P. B. X. manual switchb0aicl-P-Thc circuit functions in the genera-l manner previously 'described under Call incoming from central. oflice to P. B. X. manual switchboard (Figs. 4-and 3 in combination).

Figs. 1 and Z in combination.

' tion.

It is evident from the preceding description that the progress of any call from the P. B. X. to the central office may be divided into stages as follows: y

1. Initiating a -call connects ground to both sides of the trunk and' makes the circuit busy at the P. B. X.

2. The .linerel'ay at the central oiiice is operated over one trunk conductor and an l idle mechanical switch is seized.

3. Then the mechanical switch has been found by the trunk circuit, the latter is made busy atthe central oilice anda test circuit is connected to the other trunk con,- ductor to test the trunk circuit andl the switching mechanisms simultaneously before the calling line and switching mechanisnis are linked together.

V4.1i the trunk circuit and switching mechanism test closed the'connection is extended, andthe callingline and the switchiso ing mechanism are connected to the trunk in preparation ior dialinggbut if Athe circuits heretofore reiterred to do not test closed the circuits remain locked in the con-y locks the selector switches to the trunk cir.`

cuit at the P. VB. X. until the connection is cleared out at the cciitralotlice when the hold busy circuit is opened andthe P. B. X. circuits are restored to norn'ial.

6. The switching mechanism at central oilice is able to distinguish between'a hold busycircuit tor talking condition, and a holdbusy circuit release condition so that it will hold on the former and releaseon the latter. j y y It is also evident that on acall from the central o'Hice tothe l). B. X. thc .hold busy circuit is closedimmediately the trunk is seized so that the trunk is causedto test busy immediately V4at all points of access` at the I. B. X., even before the P. B- X. is signaled or otherwise informed t-hat a call incoming from the central oiice is in waiting. i 4

When reverse battery supervision is usedV relay 105, (Fig. l), or 409 (Fig. 4) Vas the' case may be, should be ofthe polarized type. i p

What is claimed is: l. In a machine yswitching telephone system, a calling line,.a trunk circuit, switching mechanism at either end thereof. opcrable in association therewith under control of the calling line, means at each end of the trunk for indicatingr when itis busy,V means including a relay bridged Vacross the,

trunk at the end adjacent Vto the calling line' for holding the trunk busy thereat aftei'fthe calling line disconnects while permitting the switching Vmechanism at the distantend of Vthe trunk to release, and meanscontrolled:

by said bridging relay for thereafter'releasing the remaining switching mechanism and removing the busy condition from the trunk.

2. In a machine switching telephone system, a first office, a calling line therneat, a secondoiice, a called line therein, a trunk circuit between the first and second offices,

means including one or more automatic switches in the Iirst oliice operable underl control ot the calling line for linking the calling line to the trunk circuit, means including one or moreautomatic switches in the second oflice operable over the trunkcircuit under control of thecalling line to build up a connection tothe called line, means for causing the trunk vcircuit to test busy at either end, means for releasing the switches at the second oilice when the callin@ line disconnects, means electvefwhen the calling line disconnects for maintaining the busy condition on `the trunk circuit at the first 'oilice until aiter the switches at the second olce have been released, aiid means at the tirstollce for releasing the` switches and removing the busy test trom the trunk cir' cuit? after hare been released.

p In af machine switching telephone system,` a first oliice, ai calling'line thereat, a second cilice, a called line therein, a trunk circuit between "theiirst andsecond oliices, means including one. or more automatic switches in the first oiiice opera-ble under control of the calling line for linking the calling lline to the trunk circuit, means in cluding one or more automaticswitches in the second oilice operable overl the trunk the switches atthe second office circuit under control of the'calling line toA build up a' connection to the called line," .means for causing the4 trunk circuit to test busy at either end, means for allowing 'the' switches inthe second office to release when the calling Vline disconnects while retaining the busy condition upon 'tlie'trunk at the .first office, and means eifective' when the switches in the second otiice havebeen re-v leased tor restoring the `trunk circuit to normal in the first ofiice.

4. Iii-fa machine switching telephone vsystem, a switching mechanisnna trunk circuit vaccessible thereto, means controlled bythe y trunk circuit for seizing the switching'mechl anism, and meansV included in lthe trunk'cir cuit for testing both the trunk fcircuitand the switching mechanism before extending the trunk conductorsto the switching mechanism.V p p I i 5. In a machine switching telephone system, a switch, a trunk circuit, means controlled by the trunk circuit for seizing `the switch and a testing device included in theVY trunk circuit lfor testing both the trunk cir-f cuit and thel switch before linking them' toing line for linking the line to the switch, .v Y

means controlled by Vvthe calling line for causing the switch to seize the trunk circuit, a distant switch to which the trunk has access, means in the-trunk circuit controlled by the callnglne forcausingthe trunk circuit'to seize the distant switch, and

rag

circuit and distant switch are linked to` gether.

8. In a machine switching telephone system, a switch, a trunk circuit accessible thereto, means in the trunk circuit for seizing the switch, and means in the trunk circuit tor preventing the pumping of the switch when the trunk is caused to seize it due to the existence ot' a trouble condition on the trunk.

9. In a machine switching telephone system, a calling line, a called line, a two conductor trunk circuit having` a plurality of points of access, mechanical switches opel'- able under control ot said calling line to seize said trunk circuit- 'at one point of access, another inecl'ianical switch, means responsive to the extendingl ot said calling line to said trunk for seizing said last mentioned switch, means operable under control of said calling line to set said last mentioned switch to build upa connection to said called line, means at each. end ot the trunk responsive to said trunk seizure for causing said trunk to test busy at every point of access, means responsive to the opening ot the calling line circuit for initiating the breaking down ot the connect-ion by releasing said last mentioned switch and means responsive to said breaking down operation lor releasing the 1 remaining mechanical switches and for restoring. said trunk circuit to normal.

l0. In a telephone system, a two-conductor trunk, switch mechanism at either end thereof capable ot seizing the said trunk, means at one end o'l said trunk operable yin response to the seizure of said trunk at the opposite endovera circuitiincluding only one conductor of the trunk tor rendering the trunk busy at said first mentioned end, and means at the other .end ot the trunk operable in response to seizure of the trunkat the Vopposite end over a circuit including both of the conductors 'for rendering said trunk busy at said other end.

Il. In a telephone system, a two-conductor trunk, switch mechanism at either end thereof capable of seizing said trunk. means including a relay at one end of said trunk operable in response to the seizure of said trunk at the opposite end over a circuit including only one conductor of the trunk for rendering the trunk busy at said first mentioned end, and means including a relay at the other end of the trunk operable in response to the seizure of the trunk at the opposite end over a circuit including both ot the trunk conductors for rendering said trunk busy at said other end.

12. In a telephone system, a calling line, a two-conductor trunk, switch mechanism at either end thereof operable under control of the calling line for seizing said trunk at a point at one end and for extending said trunk at a point at the opposite end, other points oli' access at both ends of said trunk whereat said trunk may be seized, means opl erableover a circuit including one trunk conductor in response to the seizure oi said trunk by the calling line at one end and extension of the trunk at the opposite end for rendering the trunk busy at the points ot access at said opposite end, and means responsive only to said seizure ot the trunk for rendering the trunk at the points at the first mentioned end busy.

13. In a telephone system, a two-conductor trunk, mechanical switches at either end thereof capable of seizingsaid trunk, another mechanical switch adapted for extending said trunk at one point after it has been seized at another point, `and means responsive to the seizure ot said trunk at one point for rendering said trunk busy at certain points o'l' access and responsive to the extension of said trunk through said second nicntioned switch lor rendering said trunk busy at other points oi' access. y

In witness whereof, 1hereunto subscribe my name this 29th day of February A. D., 1924.

ALFRED intona. 

